The invention relates to fireproof glass or ceramic glass windowpanes which have such a high thermal resistance that, when used as glazing in doors and windows, they can withstand the fire test of DIN Standard 4102 (1970) without disintegrating due to heat.
It is generally known that, in the event of an outbreak of fire in a building, the glazing in windows, doors and partitions is broken by the heat and the fragments fall out of the frames. This disintegration and fallout of glass in the event of a fire is dangerous for two reasons. On the one hand, the falling pieces can cause serious injury, and on the other hand the fire can pass through the openings thus formed in the interior of the building and spread from room to room, and also spread through exterior windows to the floors above. What catastrophes this can produce has been shown by many fires in high buildings.
The only glasses which have hitherto been used in architectural glazing which are fire resistant in accordance with DIN Standard 4102 are wire reinforced glass and glass bricks. For many applications, however, wire glass and glass bricks are unsuitable. For optical reasons, wire glass cannot be used, for example, as window glass in residential construction. Glass bricks, on account of their great weight and greatly reduced transparency, can be used only for special purposes.
In comparison with commercial structural glass, crystal plate glass or float glass, which are all very similar with respect to their thermal expansion, thermally hardened structural glass not only possesses greater mechanical strength but also greater thermal strength. Consequently, these thermally hardened glasses are used also in exterior walls in which temperature differences of up to 100.degree. to 120.degree. C can occur.
In a fire test in accordance with DIN 4102 sheet No. 2 (1970 Edition), page 3, Section 5.2.4. (FIG. 3 hereof, Curve I), plain windows and thermally hardened windows of structural glass, crystal plate glass or float glass will disintegrate within no more than 2 to 3 minutes, thus failing to fulfill requirements with regard to the prevention of the passage of fire and smoke. Wire glass and glass bricks disintegrate in 2 to 3 minutes also, but either due to the wire reinforcement or to the width of the bricks, their integrity is preserved and the passage of fire and smoke is prevented for at least 60 minutes.
The wire mesh in wire glass has furthermore always proven disadvantageous wherever it is important to be able to use the glazed opening as an escape route or for the exhausting of smoke.